Earth Day 2013 – How Green is LED Lighting?

Since 1970, Earth Day has been celebrated in the US to spotlight environmental responsibility.  Earth Day is today (April 22) and in celebration of Earth Day 2013, we’ve put together some information from the Department of Energy about the environmental benefits of LED lighting.  The DOE is under mandate from Congress to accelerate Solid State Lighting (SSL is another name for LED lighting).  With more than 80% of LEDs based on sapphire substrates, this is good news for the sapphire industry.

SSL is rapidly undergoing improvements to technology and pricing (see Tipping Point 2: Finally, A Sub $10 LED Light Bulb) and has superior energy efficiency.  The DOE estimates that, over the next two decades, it could save the country $250 billion in energy costs, reduce electricity consumption used by lighting by nearly one half, and avoid 1,800 metric tons in carbon emissions.

From the graphic below, from the DOE’s recent report, Energy Savings Potential of Solid-State Lighting in General Illumination Applications, you can see how each sector will contribute to the energy savings due to lighting.  The graphic is illuminating on two fronts.  First, there’s a 19% savings in 2020, but there’s a 46% savings in 2030.  Second, residential lighting and commercial lighting that’s lighting interiors of business, government and other organizations, show the greatest potential for savings. For example, the commercial sector contributed 60% of lighting electrical service in 2010, but by 2030, the DOE expects energy savings potential to be 35%.  You can find the discussion about it and a larger image online here.

Forecasted US Lighting Energy Consumption and Savings, 2010 to 2030







For Further Reading

Department of Energy, Energy Savings Potential of Solid-State Lighting in General Illumination Applications,

US DOE, SSL Lighting Basics,

Commercial Sapphire Spotlight – Vertical Integration in Sapphire

Rubicon Family of Sapphire Boules

Last month, Compound Semiconductor Magazine featured a contributed article about Vertical Integration in sapphire production by Raja M. Parvez, President and CEO of Rubicon Technology.  Rubicon has adopted vertical integration to set itself apart from other sapphire companies.  The article details Rubicon’s approach.

Vertical integration isn’t a new concept. It has been around since the 1800s when US Steel tycoon Andrew Carnegie introduced the vertical integration by owning virtually every part of the steel-making value chain from iron ore through steel mills to physically building the railroads.  Later, in the 1920s, Ford Motor Company decided to make the steel for their cars, popularizing the concept further.

According to Rubicon’s president and CEO Raja Parvez, vertical integration holds the key to Rubicon’s cost structure and reliable supply of high-quality products.  This integrated approach influences every step in the growth of sapphire crystals and their processing into wafers. The company’s end-to-end manufacturing capability, with strong intellectual property at each step of the manufacturing process, produces an advantageous cost structure and provides better control of product quality and delivery schedules. Vertical integration is also central to the company’s ability to grow larger and larger sapphire and be the first to market with large-diameter sapphire wafers for the LED and SoS/RFIC markets.  To date, Rubicon has shipped more than 400,000 6-inch wafers.

To read the full article, visit:

LED Lighting Spotlight: Patterned Sapphire Substrates

In the ongoing quest to make LEDs more efficient, LED chip manufacturers have developed patterned sapphire substrates (PSS).  In fact, most high-brightness LEDs are made using PSS. There are very few resources online that explain patterned sapphire substrates. Here’s a brief explanation.

PSS helps extract more light from LEDs.  A lot of light bounces back into the LED when using a polished sapphire substrate.  Researchers discovered that patterning the surface of the substrate by etching nano-scale patterns helps more light, in the form of photons, escape, improving the light generated or extracted by the LED.  It is reported that patterning can improve the extraction of light by as much as 30%.

A second important point is that patterning also improves the epitaxial growth process.  The nano-patterned surface can have a positive effect on the nitride semiconductor growth process by promoting growth of the GaN in parallel to the substrate surface, called lateral growth.  This also helps reduce the number of dislocations, the dislocation density, that can degrade performance.

LED chip manufacturers originally developed PSS.  The patterns are quite proprietary and helped the LED chip companies differentiate themselves.  Today, the sapphire industry has joined in and sapphire wafer manufacturers have begun to put patterns on sapphire wafers in partnership with the LED chip manufacturers. The patterning work is concentrated with smaller wafers in the 2 to 4-inch diameter range, but manufacturers of large diameter wafers like Rubicon Technology are beginning to develop PSS for larger wafers.

Most patterning is based on a proprietary design from the LED chip manufacturer.  The patterns can vary from cones, pyramids and flat tops and can be organized in hexagonal or trigonal patterns.  Some basic design rules based on height and height/pitch ratio have emerged, but so far, no standards exist.  Currently the most popular pattern is a cone shape, but these patterns change frequently.  Here are some sample patterns.

Sample patterns:

Sample patterns for PSS








Sample Pattern for PSS







For Further Reading

Semiconductor Today, Patterned sapphire for nitride enhancements,

Compound Semiconductor, New Wet Process For LEDs On Patterned Sapphire Boosts Efficiency,

Compound Semiconductor, Rubicon Orders Multiple Profilers For Sapphire Production,